Biochemical response and host-pathogen relation of stalk rot fungi in early stages of maize (Zea mays L.)
Stalk rot is a destructive disease in maize caused by Fusarium and Macrophomina species. A study was carried out to understand the mode of infection, host biochemical response and comparison of inoculation techniques in Fusarium verticillioides and Macrophomina phaseolina in maize. In seed inoculation experiment, high mycelia growth on seed surface lead to rotting in 36.6% of seeds inoculated by F. verticillioides and 10.0% seeds in M. phaseolina. In seedling inoculation experiment, twenty one days old seedlings raised in glasshouse were inoculated with spore suspension of both pathogens, respectively in two sets, resulting in symptoms like tip drying, necrotic lesions, chlorotic bands, pale green leaves and yellowing of margins in varying numbers. Significant result was the appearance of asymptomatic seedlings in F. verticillioides infection which was confirmed by the increase in total soluble phenols (9.39 mg/g) and total sugars (5.33 mg/g) content in comparison to the control (2.84 mg/g total soluble solid (TSS) and 2.18 mg/g total soluble phenols) and symptomatic ones. While in M. phaseolina, total contents of sugar and soluble phenols were on part in asymptomatic and control (uninfected), depicting disease escape to be the possible cause of this phenotypic expression. The study concludes that inoculation techniques for screening of genotypes play a major role. The appearance and non appearance of symptoms in infected host can mislead the identification of resistant genotypes.
Key words: Maize, Fusarium verticillioides, Macrophomina phaseolina, total soluble sugar, total soluble phenols.